Pressure-actuated valve for controlling gas flow in driers



Aug. 4, 1964 J. J. ElGE ETAI.

PRESSURE-ACTUATED VALVE FOR CONTROLLING GAS FLOW IN DRIERS Filed March 2. 1961 m w m mam N m M Wi W a IUD A My PM United States Patent 3,143,396 PRESSURE-ACTUATED VALVE FUR CON- TROLLEIG GAS FLOW IN DES John J. Eige, Redwood City, Raymond E. Lundherg, Menlo Park, and Harmon H. Woodworth, Paio Alto, Calif., assignors, by mesue assignments, to .let Stream Products, Inc., Reno, Nero, a corporation of Nevada Filed Mar. 2, 1961, Ser. No. 2,964 Claims. (Cl. 34-54) This invention relates to a gas valve and the application of such valves in a drying machine.

In many applications, it is desired to maintain a substantially constant flow of gas through a space regardless of the pressure drop across the space. For instance, in a high speed washer and dryer wherein a textile material passes through the machine between endless screen belts and is dried by the application of super-heated steam, a serious problem arises if the drying chamber is not completely filled with textiles being dried. If only a portion of the chamber is occupied, the drying becomes inefficient since substantially all of the gas flow will take place through the empty portion of the chamber. Further, in such a system using a closed loop wherein the steam is reheated and recycled, the flow rate becomes excessive if the chamber is incompletely filled, possibly overloading the blower motor and causing difficulties with temperature regulation. Additionally, when dilferent types of textile materials are present within the dryer, substantially the same condition will exist if some of the material is more porous than other material.

In accordance with the present invention, a valve is provided which is adapted to maintain a substantially constant flow rate under widely varying conditions of pressure drop across a space. In accordance with another aspect of the invention, a plurality of valves is provided within a chamber so that a constant flow rate can be maintained in all portions of the chamber despite the fact that different portions of the chamber may be subjected to different conditions.

Generally speaking, the present invention is accomplished by providing a valve having a movable vane with an orifice closing plate at the end thereof wherein one side of the vane is subjected to the full pressure of the gas stream while the other side of the vane is subjected to a reduced pressure after the gas has flowed through an orifice. Thus, the valve responds to changes in differential pressure and will be partially closed should the gas pressure increase, so that the net efiect is substantially constant gas flow through the valve regardless of changes of pressure in the valve line.

In accordance with one aspect of the invention, a novel valve biasing means is employed wherein the valve action is controlled by the combination of gravity-operated and spring-operated means whereby certain desired operating characteristics can be secured. As is hereinafter explained in detail, the desired operating characteristics can be obtained in various manners, and the combination of gravity and spring biasing is to be considered only as one illustration.

In the drawings forming part of this application:

FIGURE 1 is a view, partially in section, of a laundry dryer embodying a plurality of valves of the present invention.

FIGURE 2 is a sectional view of a valve embodying the present invention.

FIGURE 3 is a perspective View of a portion of the valve mechanism showing the arrangement of the vane therein.

Turning now to a description of the drawings by reference characters, there is shown in FIGURE 1 a laundry dryer generally designated 5 having a steam input manifold 7 connected to a line 9 which leads to a source of super-heated steam, not illustrated. Directly below the manifold 7 is a similar exhaust manifold 11 having a line 13 for withdrawing steam from the manifold, which steam may be recycled. The manifolds 7 and 11 do not fit tigh ly together but have a gap 15 therebetween through which pass two parallel mesh or screen belts, namely an upper belt 17 and a lower belt 19. Guide rollers 21 and 23 are provided for guiding the belts through the dryer. It will be understood that textile materials such as articles of clothing 25 may be placed between the belts 17 and 19 and passed through the dryer. It will be noted that in the embodiment shown the manifold 11 is broken into a series of compartments by means of the partitions 27, 29 and 31 forming compartments such as those designated 33, 35 and 37. The partitions each have a roller 39 at the top thereof which tends to support the belts as they pass through the machine and also to form a seal at the top of each compartment between the compartment and any material passing over the belts. It will be understood that a tight seal is not necessary since the valving arrangement of the present invention is not designed to cut off flow entirely but only to control flow within certain desired limits.

Each of the chambers thus formed has one of the valves of the present invention, i.e., chamber 33 has a valve 41, chamber 35 has a valve 43 and chamber 37 has a valve 45. It will be noted in FIGURE 1 that an article is passing over the chamber 33 so that the valve 41 is fully opened, while there is no article over the chamber so that the valve 43 is at its minimum opening. In chamber 37 an article occupies about half of the space over the valve so that the valve 45 is partially closed.

In FIGURES 2 and 3, the construction of the valve proper is shown in detail. In FIGURES 2 and 3, the walls 27 and 29 form the chamber 35 as described above. Situated within the chamber 35 and attached to one of the walls such as at 27 is an orifice plate 47 which extends about three-fourths of the way across the chamber and extends the entire width of the chamber. The plate 47 has one or more apertures 49 therein and the bottom of the plate is made concave adjacent the apertures as at 51 to secure a better fit with the movable plate of the valve. The valve member proper consists of an L-shaped member having a relatively long vane section 53 and a short plate section 55 at right angles thereto. The terminal end of the vane 53 is attached to a shaft 57. Also attached to the shaft 57 is a first arm 5h having an adjustable weight 61 thereon and a second arm 63 to which is attached a spring 65 held by the adjustable bracket 67. Suitable stops 69 and 71 are provided to limit the movement of the vane. In the valve described, flow is downward and the spring 65 and counter-weight 61 are arranged to hold the valve in its open position when flow is at the desired rate through the apertures 49. However, should flow increase beyond that desired, the vane 53 will be subjected to an unbalanced force, i.e., therewill be a pressure drop of gas passing through the aperture 49 so that that portion of the vane designated 53a will be subjected to a reduced gas pressure while that portion designated 53b will be subjected to the full pressure of the gas in the chamber 35. This will tend to partially close the valve. In this manner, the gas flow will be maintained substantially constant regardless of whether any material is passing through the dryer or not.

In the embodiment shown, the drying chamber is divided into a relatively small number of compartments, but it is obvious that the valves can be made smaller so that the compartment can be divided into more chambers to secure more precise control over each particular portion of the chamber. Further, the valves need not extend the entire Width of the chamber, but two or more valves can be used in side-by-side relationship so that flow will be controlled even should material be passing through only one side of the dryer.

To secure satisfactory pressure regulating characteristics, the moment caused by air pressure on the regulating valve and the restraining moment must be approximately equal at each angle of opening. Various methods can be used to secure this action such as by various combinations of weights or combinations of springs or combinations of weights and springs, acting against various lever arms. In the embodiment shown, the weight 61 exerts a substantially constant moment throughout all angles of valve openings, while the spring 65 is preloaded and acts on a moment arm which varies with angle. This has been found to give an almost perfect match between the air pressure moment and the restraining moment within the angle through which the valve operates, although, as is pointed out above, other means can be used to secure the desired operating characteristics.

We claim:

1. In a dryer for materials wherein the materials are passed through a drying chamber and subjected to the flow of gas therethrough, the improvement comprising a series of partitions dividing said chamber into a plurality of compartments and dividing the gas flow into a plurality of parallel paths flowing through said compartments, means in each of said compartments'forming an orifice through which the gas must pass, a movable vane mounted downstream from said orifice and having an orifice closing plate mounted at one end thereof, and biasing means comprising a combination of a spring and weighted lever arm for normally holding said vane to an open position, said vane being situated so that one side thereof is subjected to the full gas pressure and the other side is subjected to the reduced pressure of the gas after having passed through the orifice.

2. In a dryer for materials wherein the materials are subjected to the action of a drying fluid, the combination of means forming within the dryer a plurality of compartments'each adapted to permit flow of a portion of the drying fluid therethrough, pressure-actuated valve means for each compartment for controlling fluid flow therethrough, means in each compartment providing a flow restricting orifice causing a pressure drop of fluid flowing therethrough, the valve means for each compartment being responsive to changes occurring in the fluid pressure drop across said orifice, and biasing means for each valve means 41 for holding the same in an open position until the fluid flow through said compartment increases above a desired rate.

3. The invention as claimed in claim 2 wherein said biasing means includes a combination of means selected from the group consisting of gravity-operated means and spring-operated means.

4. The invention as claimed in claim 3 wherein said biasing means includes a combination of a spring and a weight.

5. In a dryer for materials wherein the materials are passed through a drying chamber and subjected therein to the action of a drying fluid flowing through the dryer, the combination of means forming within the dryer a plurality of compartments each having an end thereof opening into said drying chamber and each adapted to permit passage therethrough of a portion of the drying fluid flowing through the dryer, at least a plurality of said compartments being arranged so that materials passing through said drying chamber move successively past the ends of said compartments opening into said drying chamber, means for each compartment providing a flow restricting orifice causing a drop in pressure of fluid flowing therethrough, and valve means for each compartment for controlling fluid flow therethrough in response to changes occurring in the fluid pressure drop across said orifice, said valve means including a movably mounted valve member for controlling fluid flow through said orifice, said valve member having two opposed surfaces, one of said surfaces being exposed to the pressure of fluid on one side of said orifice and the other of said surfaces being exposed to the pressure of fluid on the opposite side of said.orifice, said valve member being mounted for movement in a direction to decrease fluid flow through said orifice in response to an increase occurring in the fluid pressure drop across said flow restriction, and biasing means for holding said valve member in an open position until the fluid pressure drop across said orifice increases above that resulting from a desired rate of fluid flow through said compartment.

References Cited in the file of this patent UNITED STATES PATENTS 1,546,180 Osborn July 14, 1925 2,525,535 Erismann et al Oct. 10, 1950 2,816,372 Myers Dec. 17, 1957 2,911,002 Larkfeldt Nov. 3, 1959 2,933,100 Waterfill Apr. 19, 1960 

1. IN A DRYER FOR MATERIALS WHEREIN THE MATERIALS ARE PASSED THROUGH A DRYING CHAMBER AND SUBJECTED TO THE FLOW OF GAS THERETHROUGH, THE IMPROVEMENT COMPRISING A SERIES OF PARTITIONS DIVIDING SAID CHAMBER INTO A PLURALITY OF COMPARTMENTS AND DIVIDING THE GAS FLOW INTO A PLURALITY OF PARALLEL PATHS FLOWING THROUGH SAID COMPARTMENTS, MEANS IN EACH OF SAID COMPARTMENTS FORMING AN ORIFICE THROUGH WHICH THE GAS MUST PASS, A MOVABLE VANE MOUNTED DOWNSTREAM FROM SAID ORIFICE AND HAVING AN ORIFICE CLOSING PLATE MOUNTED AT ONE END THEREOF, AND BIASING MEANS COMPRISING A COMBINATION OF A SPRING AND WEIGHTED LEVER ARM FOR NORMALLY HOLDING SAID VANE TO AN OPEN POSITION, SAID VANE BEING SITUATED SO THAT ONE SIDE THEREOF IS SUBJECTED TO THE FULL GAS PRESSURE AND THE OTHER SIDE IS SUBJECTED TO THE REDUCED PRESSURE OF THE GAS AFTER HAVING PASSED THROUGH THE ORIFICE. 